(1) Field of the Invention
The present invention relates to methods used to fabricate semiconductor devices, and more specifically to a method used to improve the adhesion of an intermetal dielectric, (IMD), layer, such as a hydrogen silsesquioxane, (HSG), layer, to underlying insulator layers.
(2) Description of Prior Art
To improve the performance of semiconductor chips, the RC, (resistance-capacitance), value, has to be decreased. The use of copper, for metal interconnect structures, has reduced the resistance component, of the RC value, when compared to more resistive metal interconnect structures, comprised with materials such as aluminum or tungsten. In addition, capacitance decreases have been achieved via use of low dielectric constant, (low k dielectrics), materials, such as hydrogen silsesquioxane, (HSQ), featuring a dielectric constant of about 2.9. HSQ layers are used to either replace silicon oxide layers, featuring a dielectric constant of about 3.9, or to be used as a component of a composite dielectric layer, comprised with a silicon oxide layer as one of the components of the composite dielectric layer.
One scenario for the use of HSQ layers, is the application of the HSQ layer on an underlying, thin silicon oxide layer. The thin silicon oxide layer, obtained via a plasma enhanced chemical vapor deposition, (PECVD), procedure, results in the thin, plasma enhanced silicon oxide, (PEOX), layer, directly overlying, and passivating, underlying metal interconnect structures. However after application of the HSQ layer, and the deposition of another, overlying PECVD silicon oxide layer, the adhesion of the HSQ layer, to the underlying thin, PEOX layer can be marginal, and delamination of the HSQ layer, from the underlying PEOX layer, can occur.
This invention will describe a plasma treatment procedure, applied to the thin, PEOX layer, prior to the application of an HSQ, resulting in improved adhesion of the HSQ layer to the underlying thin PEOX layer, eliminating, or reducing the delamination phenomena. The plasma process described in this invention can also be performed to the underlying, thin PEOX layer, prior to the application, or deposition, of other low k dielectric layers, such as fluorinated oxide layers, or fluorinated polyamide with dielectric constants between about 2.6 to 3.5. In addition this invention will describe a combination of plasma anneal treatments, one just described, performed prior to the application of the low k dielectric layer, and a second plasma treatment, applied to the low k dielectric layer, prior to the deposition of an overlying insulator layer. Prior art, such as Sheen et al, in U.S. Pat. No. 5,902,122, describe the use of a plasma nitrogen treatment, applied to an underlying silicon oxide layer, prior to the application of a spin on glass layer. That prior art however does not offer the combination of plasma treatments, with the first applied to an underlying silicon oxide layer, prior to the application of a low k dielectric layer, such as HSQ, and with the second plasma treatment applied to the low k dielectric layer, prior to the deposition of an overlying silicon oxide layer. This series of novel plasma treatments, improve the adhesion of, and to reduce the delamination of, the thicker, low k dielectric layer, from the underlying silicon oxide layer.